Jan. 28th, 2019

Jan. 28th, 2019

The holidays are over and I'm back to having a
little hobby time here and there. With the LED mod assembled and
in place, the coaxial illuminator is certainly much brighter than
the original halogen-powered unit. Of course, an LED ring light
still utterly destroys it, but the brightness level of the modded version is usable in
a lit room, where the original halogen version really wasn't. So, yay.

However... contrast is damaged somewhat? Did I get some optics dirty?

A little investigation reveals our problem is at the primary constraint in the
optical path. Specifically, the coaxial illuminator is designed to
focus down an image of the light source right at the plane of the
internal adjustable iris in order to get as much useful light through it
as possible. You can see the glowing filament clearly when the iris is nearly
closed, and it passes through cleanly with the iris open.

When the light doesn't clear the iris but shines on it
instead, the light pollutes the image. Interestingly, this means
the adjustable iris and coaxial illuminator don't really coexist
well, a problem I hadn't noticed before but yup.... sure
enough... the illuminator is only really useful with the iris
wide open.

Possibly for this reason, the slightly later SZH10 dispenses
with the adjustable iris for a fixed aperture, instead
offering the iris as an accessory 'slice' that can be
placed later in the optical path. This neatly avoids the contrast problem.

In any case, my problem is 90% a slight misalignment, easily dealt with.

That said, the square die image is just a bit too large to fit
cleanly through the round iris opening even when aligned. A
little optimization of my illuminator optics is probably called
for.

But... can I actually do better? Olympus knew what
they were doing, and if there was an obviously better lens design they'd
have used it, right?